fuzzable

Fuzzable is an adjective used in software testing to describe a system, component, or interface that can be effectively subjected to fuzz testing. A fuzzable artifact provides defined input entry points, accepts a wide range of inputs (including invalid or unexpected data), and yields observable behavior that can be analyzed for anomalies such as crashes, hangs, or security vulnerabilities.

Key characteristics include: an exposed input surface that can be programmatically exercised; tolerance for unexpected inputs; instrumentation that provides observable outcomes; and the ability to reproduce incidents for investigation. A fuzzable system also typically includes a test harness or wrapper that feeds inputs to the component and logs crashes or performance deviations.

Assessing fuzzability combines design review and hands-on testing. Engineers examine the data formats, protocols, and stateful sequences to identify fuzzing opportunities. They then run fuzzers—software tools that generate or mutate inputs—while collecting coverage data and crash reports to gauge how thoroughly the component responds to unusual inputs. Fuzzability can be enhanced by simplifying input handling, improving error reporting, and providing deterministic behavior under test.

Typical targets include parsers, decoders, protocol implementations, file format handlers, and APIs. Fuzzers may be mutation-based, generation-based, or coverage-guided, and they are often integrated with continuous testing pipelines to expose defects early.

Limitations include non-deterministic behavior, dependence on external systems, or cryptographic protections that complicate fuzzing. Fuzzability should be considered alongside other quality assurance techniques to ensure robust software.